Vitreous antimicrobial agent and antimicrobial product

ABSTRACT

A vitreous antimicrobial agent that can exhibit excellent antimicrobial properties when added to various types of resins, that has excellent discoloration resistance and hot water resistance, and that can easily be produced at a commercial scale. The vitreous antimicrobial agent includes, relative to 100 mass % of total glass components, 0.1 to 2 mass % of Ag 2 O, 40.5 to 49 mass % of ZnO, 6 to 9.5 mass % of SiO 2 , 30.5 to 39.5 mass % of B 2 O 3 , 2 to 10 mass % of an alkaline earth metal oxide, and 6 to 7.5 mass % of Na 2 O; the vitreous antimicrobial agent comprising, in addition to these, 0.01 to 5 mass % of CeO 2  as necessary. An antimicrobial resin composition and an antimicrobial product including the vitreous antimicrobial agent.

The present application is a national stage entry of PCT/JP04/00661filed 26 Jan. 2004.

TECHNICAL FIELD

The present invention relates to a silver- and zinc-containing vitreousantimicrobial agent and to an antimicrobial resin composition and anantimicrobial product comprising the antimicrobial agent.

BACKGROUND ART

As conventional inorganic antimicrobial agents, those in which anantimicrobial metal such as silver or copper is supported on apatite,zeolite, glass, zirconium phosphate, silica gel, etc. are known.Compared with organic antimicrobial agents, they have high safety, anddo not evaporate or decompose, thus having a long-lasting antimicrobialeffect and, moreover, they have excellent heat resistance. Because ofthis, antimicrobial resin compositions obtained by mixing theseantimicrobial agents with various types of polymer compounds are moldedinto antimicrobial products in the form of various types of moldings,fibers, and films and are used in various types of applications.

Among these, vitreous antimicrobial agents comprising an antimicrobialmetal such as silver, copper, or zinc have the characteristics that theglass grain size, the refractive index, and leaching properties ofantimicrobial metal can easily be controlled according to the intendedapplication, and they are therefore added to antimicrobial resincompositions for various types of applications.

For example, a silver-containing vitreous antimicrobial agent has beenproposed (ref., e.g. JP-A-03-124810). Furthermore, a vitreousantimicrobial agent comprising a high concentration of zinc has beenproposed (ref., e.g. JP-A-2001-26438).

Although the conventional silver-containing vitreous antimicrobial agent(also called a silver-based vitreous antimicrobial agent) has theadvantage that a high antimicrobial effect can be obtained with arelatively low concentration of silver, there are the problems that, dueto heat when kneading with a resin or due to exposure to UV rays afterprocessing of the resin, degradation and deterioration of the resinitself are accelerated or the resin product is discolored, and theexcellent characteristics of the resin product itself are thus oftenimpaired. Furthermore, when the vitreous antimicrobial agent comprisingsilver alone as the antimicrobial component is kneaded with certainresins, such as an ABS resin or an acrylic resin, it is difficult forthe antimicrobial effect to be exhibited.

On the other hand, when the vitreous antimicrobial agent comprising ahigh concentration of zinc alone is kneaded with a resin, it causeslittle degradation, deterioration, or discoloration of the resin, butcompared with the silver-containing glass, the antimicrobial propertiescan be poor in some cases, and if an attempt is made to make the resincomposition exhibit an adequate antimicrobial effect, it is necessary toincrease the amount added to the resin, and as a result there is theproblem that the physical properties of the resin itself are degraded.

In order to solve these problems, a vitreous antimicrobial agentcomprising both silver and zinc has been proposed.

As an example of a composition comprising phosphoric acid, a vitreousantimicrobial agent comprising 0.2 to 5 wt % of Ag₂O, 1 to 50 wt % ofZnO, 30 to 80 wt % of P₂O₅, 1 to 20 wt % of CaO, and 0.1 to 5 wt % ofCeO₂ has been proposed (ref. e.g. JP-A-2000-191339). A vitreousantimicrobial agent comprising 0.1 to 5 wt % of Ag₂O, 1 to 50 mol % ofMgO+CaO+BaO+ZnO, 30 to 60 mol % of P₂O₅, 2 to 40 mol % of B₂O₃, at most15 mol % of Al₂O₃, and at most 15 mol % of an alkali metal oxide hasalso been proposed (ref., e.g. JP-A-2001-247726). A vitreousantimicrobial agent comprising 0.03 to 5 mol % of Ag₂O, 0 to 30 mol % ofZnO+BaO, 0 to 20 mol % of B₂O₃, 0 to 2.5 wt % of TiO₂+CeO, 0 to 5 mol %of SiO₂, 20 to 55 mol % of MgO+CaO, 5 to 25 mol % of Na₂O, 40 to 55 mol% of P₂O₅, and 0 to 5 mol % of PbO has also been proposed (ref., e.g.JP-A-8-48539).

As an example of a composition comprising no phosphoric acid, a solublevitreous antimicrobial agent comprising 20 to 50 wt % of B₂O₃, 50 to 80wt % of ZnO, at most 10 wt % of an alkaline earth metal oxide, and atmost 2 wt % of Ag₂O has been proposed (ref., e.g. JP-A-2000-281380). Avitreous antimicrobial agent comprising 0.1 to 5 wt % of Ag₂O, 35 to 60wt % of ZnO+MgO+CaO+BaO, 10 to 50 wt % of SiO₂, 0 to 20 wt % of Al₂O₃, 0to 20 wt % of Na₂O+K₂O+Li₂O, 10 to 54 wt % of B₂O₃, 0 to 10 wt % ofTiO₂, and 0 to 10 wt % of La₂O₃ has also been proposed (ref., e.g.JP-A-2000-302478). A vitreous antimicrobial agent comprising 0.05 to 5wt % of Ag₂O, 0 to 30 wt % of ZnO, 0 to 20 wt % of MgO+CaO+BaO, 10 to 60wt % of SiO₂, 0 to 20 wt % of Al₂O₃, 0 to 4.9 wt % of Na₂O+K₂O+Li₂O, and10 to 60 wt % of B₂O₃ has also been proposed (ref., e.g.JP-A-2000-203876).

However, it is known that the vitreous antimicrobial agent comprisingsilver and, as a main component, P₂O₅, has poor hot water resistance.The glass comprising B₂O₃ as a main component has high hardness, ittherefore abrades a metal surface of a mixer or a resin molder used forkneading it with a resin, and there is thus the problem that a metalpowder formed by scraping contaminates the resin composition, therebydarkening the color of a final resin product. When a large amount ofB₂O₃ is contained in the glass, as is the case for that comprising P₂O₅as a main component, there might be problems caused by poor hot waterresistance.

In order for a high antimicrobial effect, which can be provided forvarious types of processed resin products, to be exhibited, a glasscomposition having as high a concentration of zinc as possible and anappropriate amount of silver is effective. However, unless theconcentrations of P₂O₅ and B₂O₃, which are glass framework-formingcomponents, are reduced as much as possible, the relative ZnOconcentration in the glass composition cannot be increased, and theproblems with regard to hot water resistance, discoloration, andhardness when added to a processed resin product cannot be eliminated.Furthermore, a composition comprising a high concentration of zinc, aswell as silver, which is easily reducible, can easily be prepared in asmall amount such as at laboratory scale, but when commercial productionof on the order of at least a few hundred kg is carried out, there isthe problem that the glass is colored. It is therefore not easy tomass-produce an antimicrobial agent comprising a glass comprisingsilver, which has a high antimicrobial effect, and a high concentrationof zinc.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a vitreousantimicrobial agent that can exhibit excellent antimicrobial propertieswhen added to various types of resins, which has excellent discolorationresistance and hot water resistance, and which can easily be produced ona commercial scale. It is another object thereof to provide anantimicrobial resin composition and an antimicrobial product comprisingthe vitreous antimicrobial agent.

As a result of an intensive investigation by the present inventors inorder to attain the above-mentioned objects, it has been found that aspecified glass having a limited glass composition range can attain theabove-mentioned objects, and the present invention has thus beenaccomplished. That is, the present invention relates to a vitreousantimicrobial agent comprising, relative to 100 mass % of total glasscomponents, 0.1 to 2 mass % of Ag₂O, 40.5 to 49 mass % of ZnO, 6 to 9.5mass % of SiO₂, 30.5 to 39.5 mass % of B₂O₃, 2 to 10 mass % of analkaline earth metal oxide, and 6 to 7.5 mass % of Na₂O, to a vitreousantimicrobial agent comprising, in addition to these, 0.01 to 5 mass %of CeO₂ as necessary, to an antimicrobial resin composition thatincludes the vitreous antimicrobial agent, and to an antimicrobialproduct that includes the vitreous antimicrobial agent.

The present invention has been achieved based on the above-mentionedunderstanding, and representative examples thereof are cited below.

-   1. A vitreous antimicrobial agent comprising, relative to 100 mass %    of total glass components, 0.1 to 2 mass % of Ag₂O, 40.5 to 49 mass    % of ZnO, 6 to 9.5 mass % of SiO₂, 30.5 to 39.5 mass % of B₂O₃, 2 to    10 mass % of an alkaline earth metal oxide, and 6 to 7.5 mass % of    Na₂O.-   2. The vitreous antimicrobial agent according to 1 above, wherein    the glass component further comprises 0.01 to 5 mass % of CeO₂.-   3. The vitreous antimicrobial agent according to 1 above, wherein    the vitreous antimicrobial agent is a powder and has an average    particle size of 0.1 to 30 μm.-   4. An antimicrobial resin composition comprising the vitreous    antimicrobial agent according to any one of 1 to 3 above in an    amount at which an antimicrobial function is exhibited.-   5. An antimicrobial resin composition comprising the vitreous    antimicrobial agent according to any one of 1 to 3 above at 0.03 to    5 parts by mass relative to 100 parts by mass of the antimicrobial    resin composition.-   6. An antimicrobial product comprising the vitreous antimicrobial    agent according to any one of 1 to 3 above.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is explained in detail below.

Vitreous Antimicrobial Agent

The antimicrobial agent of the present invention is a vitreousantimicrobial agent comprising at least Ag and Zn; a vitreousantimicrobial agent comprising, relative to 100 mass % of total glasscomponents, 0.1 to 2 mass % of Ag₂O, 40.5 to 49 mass % of ZnO, 6 to 9.5mass % of SiO₂, 30.5 to 39.5 mass % of B₂O₃, 2 to 10 mass % of analkaline earth metal oxide, and 6 to 7.5 mass % of Na₂O; and a vitreousantimicrobial agent comprising in addition to the above 0.01 to 5 mass %of CeO₂ as necessary (hereinafter, when the percentage content of eachof the component is mentioned, it is a percentage content relative to100 mass % of the total glass components).

The glass components referred to in the present invention are Ag₂O, ZnO,SiO₂, B₂O₃, an alkaline earth metal oxide, and Na₂O, and include CeO₂ asnecessary. The vitreous antimicrobial agent may include, in addition tothese glass components, various types of oxidizing agents, additives,and other glass-forming components.

In the vitreous antimicrobial agent of the present invention, thepercentage content of Ag₂O, which is a component imparting antimicrobialperformance, is 0.1 to 2 mass %, preferably 0.4 to 1.5 mass %, and morepreferably 0.6 to 1.4 mass %. It is difficult to convert Ag₂O into aglass, and when it is added at more than 2 mass %, silver that has notbeen converted into a glass might be deposited as a metal. This alsocauses the problem that the metallic silver thus deposited might colorthe glass. On the other hand, when Ag₂O is less than 0.1 mass %, theantimicrobial properties of the vitreous antimicrobial agent of thepresent invention might become insufficient.

The percentage content of ZnO, which together with Ag₂O is a componentthat imparts antimicrobial performance to the vitreous antimicrobialagent of the present invention, is 40.5 to 49 mass %, preferably 42 to48.5 mass %, and more preferably 43 to 48 mass %. If ZnO is added atmore than 49 mass %, it is extremely difficult to form a glass, andthere is the problem that when a molten glass is cooled during massproduction the glass might be colored. On the other hand, if ZnO is lessthan 40.5 mass %, the antimicrobial properties of the glass of thepresent invention might become insufficient.

The SiO₂ component in the vitreous antimicrobial agent of the presentinvention is a component that forms a glass framework, and thepercentage content of SiO₂ in the vitreous antimicrobial agent of thepresent invention is 6 to 9.5 mass %, preferably 6.5 to 9 mass %, andmore preferably 7 to 8.5 mass %. If SiO₂ is added at more than 9.5 mass%, a processed resin product to which this vitreous antimicrobial agentis added might have difficulty in exhibiting antimicrobial propertiesand, in particular, antimicrobial properties after a hot waterresistance test. On the other hand, if SiO₂ is less than 6 mass %, itmight become difficult to form a glass.

The B₂O₃ component in the vitreous antimicrobial agent of the presentinvention is a component that forms a glass framework, and thepercentage content of B₂O₃ in the vitreous antimicrobial agent of thepresent invention is 30.5 to 39.5 mass %, preferably 30.9 to 35.5 mass%, and more preferably 31.0 to 34.5 mass %. If B₂O₃ is added at morethan 39.5 mass %, the color of a processed resin product to which thisvitreous antimicrobial agent is added becomes blackish and tends todarken, and since the relative content of the antimicrobial componentZnO decreases it might become difficult for antimicrobial properties tobe exhibited and, in particular, antimicrobial properties after a hotwater or hydrothermal treatment. On the other hand, if B₂O₃ is less than30.5 mass %, it is extremely difficult to form a glass, and when amolten glass is cooled during mass production there is the problem thatthe glass might be colored. In addition, it might be difficult forantimicrobial properties to be exhibited after a hot water orhydrothermal treatment.

Examples of the alkaline earth metal oxide in the vitreous antimicrobialagent of the present invention include MgO, CaO, SrO, and BaO, and CaOand BaO are preferable when the ease of forming a glass and theresistance to coloration of the glass itself are taken intoconsideration. The percentage content of the alkaline earth metal oxidein the vitreous antimicrobial agent is 2 to 10 mass %, preferably 3 to 8mass %, and more preferably 4 to 7.5 mass %. If the vitreousantimicrobial agent contains more than 10 mass % of the alkaline earthmetal oxide, since the relative proportion of the antimicrobialcomponent ZnO, etc., is decreased, it might become difficult for theantimicrobial effect to be exhibited, and since the proportions of theglass framework-forming components B₂O₃ and SiO₂ decrease, it mightbecome difficult to form a glass. On the other hand, if the alkalineearth metal oxide is less than 2 mass %, it might also become difficultto form a glass.

The percentage content of Na₂O in the vitreous antimicrobial agent ofthe present invention is 6 to 7.5 mass %. If the vitreous antimicrobialagent contains more than 7.5 mass % of Na₂O, since the relativeproportion of the antimicrobial component ZnO, etc., is decreased, itmight become difficult for the antimicrobial effect to be exhibited, andsince the proportions of the glass framework-forming components B₂O₃ andSiO₂ decrease, it might become difficult to form a glass. On the otherhand, if the Na₂O is less than 6 mass %, the antimicrobial effect mightnot be exhibited sufficiently.

The percentage content of CeO₂ in the vitreous antimicrobial agent ofthe present invention is preferably 0.01 to 5 mass %, and morepreferably 0.01 to 2 mass %. If the vitreous antimicrobial agentcontains more than 5 mass % of CeO₂, since the relative proportions ofother essential vitreous antimicrobial agent components decrease, itmight become difficult for the antimicrobial effect to be exhibited, andsince the proportions of glass framework-forming components decrease, itmight become difficult to form a glass. On the other hand, if no CeO₂ iscontained, the glass itself might be easily colored.

Since the vitreous antimicrobial agent of the present invention containslittle glass framework-forming components, it might be difficult to forma glass. Furthermore, since Ag₂O, which is easily reduced, is added,there is a tendency for coloration or for it to be difficult to form aglass. Hence, by adding a specified oxidizing agent to a startingmaterial formulation of the vitreous antimicrobial agent it is possibleto prepare a vitreous antimicrobial agent in which Ag₂O is resistant toreduction, coloration is prevented, and the antimicrobial activity isstabilized.

Preferred components of the oxidizing agent include nitrates such asammonium nitrate, sodium nitrate, zinc nitrate, silver nitrate, bariumnitrate, calcium nitrate, and magnesium nitrate, antimony oxide, and anarsenic compound, and the nitrates are most preferable from theviewpoint of safety and absence of the influence of residues in theglass. The percentage content of the oxidizing agent in the vitreousantimicrobial agent is at most 20 mass % relative to the glasscomponent. When zinc nitrate or silver nitrate is used as the oxidizingagent, it is added while taking into consideration the concentrations ofZnO and AgO₂ in the vitreous antimicrobial agent.

Essential glass components in the present invention include Ag₂O, ZnO,SiO₂, B₂O₃, an alkaline earth metal oxide, and Na₂O, and as long as eachof the above-mentioned glass components is in the correspondingcompositional range of the present invention, another glass-formingcomponent may be added as required. However, Al₂O₃ and P₂O₅ areundesirable components since they are highly likely to degrade the hotwater resistance of the vitreous antimicrobial agent of the presentinvention. Preferred examples include ZrO₂ and TiO₂; and if desired Li₂Oand K₂O and a so-called ‘modifying component’, for example, a fluorinecompound such as sodium fluoride or aluminum fluoride, can be added asappropriate. They are effective in accelerating melting of the glass andimproving moldability, but if a large amount of glass-forming componentand/or modifying component is added to the vitreous antimicrobial agent,there is a possibility that the hot water resistance of the glass mightbe degraded or the characteristics of the present invention might beimpaired, and the content is therefore preferably at most 2 mass %relative to the glass components, and more preferably at most 1 mass %.

When the vitreous antimicrobial agent of the present invention is addedto a resin, the agent is usually used in the form of a powder, and it isgenerally preferable for the average particle size to be equal to orless than 30 μm from the viewpoint of dispersion in the resin; inparticular, when the agent is processed into a product such as a fiber,a paint, or a film, it is preferable to employ an agent having anaverage particle size of equal to or less than 15 μm and a maximumparticle size of equal to or less than 20 μm so as not to degrade thephysical properties of the product. The finer the particle size of thevitreous antimicrobial agent of the present invention, the easier it isfor discoloration of the resin and for process failures such assecondary aggregation to occur, and the average particle size istherefore preferably between 3 μm and 15 μm. In the vitreousantimicrobial agent of the present invention, when the grain size isadjusted by grinding glass lumps obtained by melting and cooling, thereis a possibility of contamination with coarse material, and it istherefore preferable to remove the coarse material by passing through asieve after grinding, etc.

The average particle size referred to in the present invention is anaverage particle size on a volume basis measured by a laser diffractionmethod.

When producing the vitreous antimicrobial agent of the presentinvention, a known production process can be employed. In general, aglass starting material formulation or a mixture of this startingmaterial formulation and an oxidizing agent is melted in a meltingfurnace at 900° C. to 1700° C., the melt is rapidly cooled, and the lumpglass thus obtained is ground to give a desired glass powder.

In order for excellent antimicrobial properties to be exhibited comparedwith conventional products, the antimicrobial agent of the presentinvention has a high content of ZnO, and has lower concentrations ofSiO₂ and B₂O₃, which are glass framework-forming components, comparedwith conventional vitreous antimicrobial agents, and it might bedifficult to form a glass, particularly during mass production on acommercial basis. Taking this into consideration, a glass is obtainedeasily by melting at an appropriate melting temperature and employingrapid cooling means suitable for the cooling characteristics of themelt. When the cooling speed is slow, part of the starting materialcomponents might precipitate, thus causing coloration, or they might notbecome a glass in parts, thus forming a nonuniform composition.

In order to enhance the cooling effect, increasing the contact areabetween the melt and a cooling body is effective; for example, anextremely high cooling effect can be achieved by passing the moltenglass at high speed through metal rollers cooled by means of a coolingmedium such as water, and in accordance with this cooling method it iseasy to form a glass. When cooling is carried out by this method, sincethe glass coming out between the rollers is molded into a thin sheet, itis extremely easy to grind it into a powder.

When the antimicrobial agent of the present invention is kneaded into aresin, the antimicrobial performance is exhibited by the antimicrobialagent that is present on the surface of a resin molding, and when theresin molding is subjected to rubbing, cleaning, or washing, thisantimicrobial agent might come off from the surface of the resinmolding. When the extent to which it comes off is high, theantimicrobial effect deteriorates and the effect might disappear in avery short period of time.

When the antimicrobial agent of the present invention is kneaded into aresin, etc., by enhancing contact or adhesion between the antimicrobialagent and the resin, it is possible to improve the dispersibility of theantimicrobial agent and to prevent the antimicrobial agent from comingoff from the surface of the resin composition. In this case, it is alsopossible to treat the surface of the vitreous antimicrobial agent powderwith a surface treatment agent such as a silane coupling agent or asilicone oil.

With regard to the surface treatment agent used in the presentinvention, the most suitable one may be selected appropriately accordingto the intended application, the type of resin, the processing method,etc., and any treatment agent may be used as long as it isconventionally used for the surface treatment of an inorganic powder,and is not particularly limited.

Specific examples of the surface treatment agent include vinylsilanessuch as vinyltriethoxysilane and vinyltrimethoxysilane;(meth)acryloxysilanes and glycidoxysilanes such asγ-methacryloxypropyltrimethoxysilane andγ-glycidoxypropyltrimethoxysilane; coupling agents such astetraethoxysilane, titanium tetraisopropoxide, and aluminum ethylate;and silicone oils such as dimethyl silicone, methylphenyl silicone,methyl hydrogen silicone, reactive silicone, and non-reactive silicone.

The surface treatment method is not particularly limited, and any methodthat is conventionally known as a surface treatment method for aninorganic powder may be used. Examples thereof include a dry method, awet method, a spray method, and a gasification method. As an efficientsurface treatment method, there is a method in which, when grinding aglass into a powder, a mixture of lump glass and the surface treatmentagent is ground in a grinder. Use of this method allows the surfacetreatment to be carried out at the same time.

The antimicrobial agent of the present invention may be used singly, butwhen it is used in combination with another antimicrobial agent, theantimicrobial properties can be further enhanced so as to suit varioustypes of processing and required performance.

With regard to an antimicrobial agent used in combination with theantimicrobial agent of the present invention, an inorganic compoundhaving silver and/or zinc supported thereon or an organic antimicrobialagent can be used. Examples of an inorganic compound on which silverand/or zinc are to be supported are as follows. That is, there areinorganic absorbents such as activated alumina and silica gel, andinorganic ion exchangers such as zeolite, calcium phosphate, zirconiumphosphate, titanium phosphate, potassium titanate, hydrated bismuthoxide, hydrated zirconium oxide, and hydrotalcite. Furthermore, theantimicrobial effect can be further improved by adding zinc oxide or avitreous antimicrobial agent that has a different glass composition fromthat of the vitreous antimicrobial agent of the present invention andthat has a different particle size, solubility, etc.

It is also possible to improve rapid-acting properties or antimoldeffect by adding an organic antimicrobial agent or an antimold agent.The organic antimicrobial agent is not particularly limited, andexamples thereof are as follows. That is, there are quaternary ammoniumsalt-based compounds, glycerol fatty acid esters (e.g. fatty acidmonoglycerides), biguanide-based compounds, bronopol, phenol-basedcompounds, anilide-based compounds, iodine-based compounds,imidazole-based compounds, thiazole-based compounds, isothiazolone-basedcompounds, triazine-based compounds, nitrile-based compounds, chitosan,tropolone-based compounds, and organometallic-based compounds (zincpyrithione, OBPA).

In order to improve the kneading processability with a resin and otherphysical properties, various types of additives may be added to theantimicrobial agent of the present invention as necessary. Specificexamples thereof include a pigment such as zinc oxide or titanium oxide,an inorganic ion exchanger such as zirconium phosphate or zeolite, adye, an antioxidant, a light stabilizer, a flame retardant, anantistatic agent, a foaming agent, an impact modifier, a glass fiber, alubricant such as a metal soap, a desiccant, a filler, a coupling agent,a nucleating agent, a flowability improving agent, a deodorant, woodflour, an antimold agent, an antifoulant, a corrosion inhibitor, a metalpowder, a UV absorber, and a UV shielding agent.

An antimicrobial resin composition can easily be obtained by adding theantimicrobial agent of the present invention to a resin. The type ofresin that can be used is not particularly limited; the resin may be anyof a natural resin, a synthetic resin, and a semi-synthetic resin, andthe resin may be either a thermoplastic resin or a thermosetting resin.The resin may be any one of a molding resin, a fiber resin, and a rubberresin, and specific examples of the resin include molding or fiberresins such as polyethylene, polypropylene, vinyl chloride, ABS resin,AS resin, MBS resin, nylon resin, polyester, polyvinylidene chloride,polystyrene, polyacetal, polycarbonate, PBT, acrylic resin, fluorineresin, polyurethane elastomer, polyester elastomer, melamine, urearesin, ethylene tetrafluoride resin, unsaturated polyester resin, rayon,acetate, acrylic, polyvinyl alcohol, cupra, triacetate, and vinylidene,and rubber resins such as natural rubber, silicone rubber, styrenebutadiene rubber, ethylene propylene rubber, fluorine rubber, nitrilerubber, chlorosulfonated polyethylene rubber, butadiene rubber,synthetic natural rubber, butyl rubber, urethane rubber, and acrylicrubber. The antimicrobial agent of the present invention may be formedinto a composite with a fiber such as a natural fiber, thus giving anantimicrobial fiber.

The percentage content of the antimicrobial agent of the presentinvention in the antimicrobial resin composition of the presentinvention is preferably 0.03 to 5 parts by mass relative to 100 parts bymass of the antimicrobial resin composition, and more preferably 0.1 to2.0 parts by mass. If it is less than 0.03 parts by mass, theantimicrobial properties of the antimicrobial resin composition might beinsufficient, and on the other hand if it is present at more than 5parts by mass, there is hardly any further improvement of theantimicrobial effect, it is not cost-effective, and the physicalproperties of the resin might be greatly degraded.

A method for adding the antimicrobial agent of the present invention toa resin and processing into a resin molding may be any known method. Forexample, there are (1) a method in which an attachment agent forenhancing the adhesion between an antimicrobial agent powder and a resinor a dispersant for improving the dispersibility of the antimicrobialagent powder is used, and mixing with the resin in the form of pelletsor a powder is carried out directly in a mixer, (2) a method in whichmixing is carried out as described above, the mixture is molded intopellets using an extruder, and this molding is then added to resinpellets, (3) a method in which the antimicrobial agent is molded intohigh concentration pellets using a wax, etc., and the pellets thusmolded are then added to resin pellets, and (4) a method in which apaste composition is prepared by mixing and dispersing the antimicrobialagent in a highly viscous liquid such as a polyol, and this paste isthen added to resin pellets.

When molding the above-mentioned antimicrobial resin composition, anyknown processing techniques and equipment may be used according to thecharacteristics of various types of resins. Preparation can be easilycarried out by a mixing, addition, or kneading method while heating atan appropriate temperature and applying an appropriate increased ordecreased pressure; specific operations may be carried out by a standardmethod, and moldings in various forms such as lump, sponge, film, sheet,filament, pipe, or a composite thereof may be obtained.

With regard to the antimicrobial product thus obtained, since theantimicrobial agent of the present invention, which is a component ofthe antimicrobial product, has excellent antimicrobial properties anddiscoloration resistance, it does not deteriorate during mixing of theantimicrobial agent and the resin, during subsequent storage of theantimicrobial resin composition, or during application of the product.

The form in which the antimicrobial agent of the present invention isused is not particularly limited, and it is not limited to being addedto a resin molding or a polymer compound. It may be mixed, according tothe intended application where antimold, antialgal, and antibacterialproperties are required, with another component as appropriate or may bemade into a composite with another material. For example, it may be usedin various forms such as a powder, a powder-containing dispersion,granules, an aerosol, or a liquid.

Application

The antimicrobial agent of the present invention can be used in variousfields where antimold, antialgal, and antibacterial properties arerequired, that is, it can be used as an electrical appliance, a kitchenproduct, a fiber product, a building material product, a toiletryproduct, a paper product, a toy, a leather product, stationery, andother products.

To illustrate more specific applications, examples of the electricappliances include dish washers, dish dryers, refrigerators, washingmachines, pots, televisions, personal computers, radio cassettes,cameras, video cameras, water purifiers, rice cookers, vegetablecutters, cash registers, bedding dryers, Faxes, ventilators, andair-conditioners, and examples of the kitchen products includetableware, chopping boards, straw cutters, trays, chopsticks, teapots,thermos bottles, knives, ladle handles, turners, lunch boxes, ricespoons, bowls, colanders, sink strainers, scouring brush containers,bins, and draining bags.

Examples of the fiber products include shower curtains, mattressfillings, air-conditioner filters, stockings, socks, napkins, sheets,bedding covers, pillows, gloves, aprons, curtains, diapers, bandages,masks, and sportswear, and examples of the building materials includedecorative boards, wall paper, flooring boards, window films, handles,carpets, mats, artificial marble, handrails, jointing, tiles, and waxes.Examples of the toiletry products include toilet seats, bathtubs, tiles,potties, bins, toilet brushes, bathtub covers, pumice stones, soapcontainers, bathroom chairs, linen baskets, showers, and basins,examples of the paper products include wrapping paper, powder paper,medicine boxes, sketch books, patient charts, notebooks, and origamipaper, and examples of the toys include dolls, soft toys, papier-mache,blocks, and puzzles.

Examples of the leather products include shoes, bags, belts, watchstraps, interior products, chairs, gloves, and hanging straps, andexamples of the stationery include ball-point pens, mechanical pencils,pencils, rubbers, crayons, paper, diaries, floppy disks, rulers, labels(e.g., Post-it), and staplers.

Examples of the other products include insoles, cosmetics containers,scouring brushes, powder puffs, hearing aids, musical instruments,cigarette filters, adhesive paper sheets for cleaning, hanging straphandles, sponges, kitchen towels, cards, microphones, hairdressingequipment, vending machines, razors, telephones, medical thermometers,stethoscopes, slippers, clothing cases, toothbrushes, sandpit sand, foodwrapping films, antimicrobial sprays, and paint.

Effect

The vitreous antimicrobial agent of the present invention comprising ahigh concentration of ZnO and an appropriate amount of Ag₂O has a highantimicrobial effect, and is useful as an antimicrobial agent that canbe used with various types of resins. ZnO exhibits an effect in a widevariety of resins and easily exhibits an effect on Staphylococcusaureus, and Ag₂O tends to particularly easily exhibit an effect with anolefin resin with regard to the type of resin and on E. coli with regardto the type of microbe. It is surmised that the antimicrobial agentcomprising these two microbial components at high concentrationsexhibits a high antimicrobial effect. However, when commercialproduction of on the order of at least a few hundred kg is carried out,there are restrictions on the contents of zinc and silver and the amountof other glass-forming components added, and the glass might be coloredwhen a specific mixture ratio is not used. On the other hand, if SiO₂and B₂O₃, which are necessary as glass framework-forming components inorder to form uniform glass, are added in large amounts, there is atendency for the exhibition of a high antimicrobial effect to beinhibited. As a result of an intensive investigation, a vitreousantimicrobial agent having a high antimicrobial effect can be obtainedby minimizing the percentage contents of SiO₂ and B₂O₃ and addingappropriate amounts of an alkaline earth metal oxide and Na₂O. Since anappropriate amount of Ag₂O, which is difficult to make into a glass andis easily reduced, is added to a glass starting material mixture, byadding CeO₂ thereto the vitreous antimicrobial agent can be obtainedstably.

INDUSTRIAL APPLICABILITY

By strictly controlling the composition of the glass component, thesilver- and zinc-containing vitreous antimicrobial agent of the presentinvention can be produced at a commercial scale without coloration. Theantimicrobial agent of the present invention has a high antimicrobialeffect, can maintain the antimicrobial effect in various types of resinsfor a long period of time, and has coloration resistance, and istherefore very useful as an antimicrobial agent for use in a wide rangeof applications.

Furthermore, by adding the antimicrobial agent of the present inventionto a resin, an antimicrobial resin composition that exhibits excellentlong-lasting performance with respect to antimicrobial properties,discoloration resistance, and hot water resistance can easily beobtained. Moreover, an antimicrobial product comprising theantimicrobial agent of the present invention has excellent antimicrobialproperties, discoloration resistance, and durability.

EXAMPLES

The present invention is explained in further detail below by referenceto Examples, but the present invention should not be construed as beinglimited thereby. The values in Table 1 are mass %.

Example 1 Preparation of Vitreous Antimicrobial Agent

600 kg of a glass starting material formulation having the compositionof Example 1 shown in Table 1 was heated and melted at 1100° C. to 1300°C. After melting, cooling was carried out, and the glass thus obtainedwas dry-ground using a ball mill to give a vitreous antimicrobial agentpowder having an average particle size of about 9 μm.

Example 2 Preparation of Vitreous Antimicrobial Agent

600 kg of a glass starting material formulation having the compositionof Example 2 shown in Table 1 was subjected to the same operation as inExample 1 to give a vitreous antimicrobial agent powder.

Comparative Example 1 to Comparative Example 9

For Comparative Examples 1, 2, 5, and 6, the procedure of Example 1 wasrepeated except that glass starting material formulations (100 kg each)having the compositions shown in Table 1 were used to give vitreouspowders. For Comparative Examples 3, 4, 7, 8, and 9, the procedure ofExample 1 was repeated except that glass starting material formulationshaving the compositions shown in Table 1 were used to give vitreouspowders.

For Comparative Examples 3 and 4, the glass was partially colored paleyellow during cooling after melting, and for Comparative Examples 8 and9, the entire glass was colored pale yellow during cooling aftermelting. When the colored glass was used for a white to pale colorprocessed resin product, the color of the processed resin product waschanged to yellow and therefore could not be used often in practice, butthe glass was subjected to the various types of evaluation below.

TABLE 1 Ag₂O ZnO SiO₂ B₂O₃ P₂O₅ CaO BaO Na₂O CeO₂ Ex. 1 1.2 48.0 7.531.6 5.0 6.3 0.4 Ex. 2 0.7 43.3 8.0 34.0 3.0 4.0 7.0 Comp. 0.0 49.2 7.531.6 5.0 6.3 0.4 Ex. 1 Comp. 1.2 37.0 9.5 36.6 5.0 3.0 7.3 0.4 Ex. 2Comp. 1.2 46.9 10.5 31.6 3.5 6.3 Ex. 3 Comp. 1.2 48.0 8.5 29.6 6.0 6.30.4 Ex. 4 Comp. 1.2 48.0 7.5 31.6 5.0 6.3 0.4 Ex. 5 Comp. 1.2 42.0 7.532.0 5.0 6.0 6.3 Ex. 6 Comp. 1.2 48.0 6.4 32.0 3.5 8.9 Ex. 7 Comp. 1.251.0 6.4 31.6 3.5 6.3 Ex. 8 Comp. 2.5 46.7 7.5 31.6 5.0 6.3 0.4 Ex. 9

Example 3 Preparation of Test Molding Plate, Coloration, AntimicrobialTest, Hot Water Resistance Test

0.5 mass % of the vitreous antimicrobial agents obtained in Examples 1and 2 and Comparative Examples 1 to 9 were added to a polypropyleneresin (Grand Polypro J707Z, manufactured by Grand Polymer Co., Ltd.),and the mixtures were injection-molded at a molding temperature of 240°C. using an M-50AII-DM injection molder manufactured by Meiki Co., Ltd.to give 11 cm×11 cm×2 mm evaluation molding plates (Nos. 1 to 11).

For comparison, the polypropylene resin alone was injection-molded inthe same manner without adding any glass to give a comparative moldingplate (No. X).

Furthermore, the antimicrobial activity (initial antimicrobial effectand antimicrobial effect after immersion in hot water) of the moldingplates was evaluated in accordance with JIS Z2801. The detailedprocedure of the method for evaluating the antimicrobial activity was asfollows.

Various types of resin molding plates were cut into dimensions of 5 cm×5cm, and the surface thereof was wiped with ethanol to give evaluationsamples. As test microbes, E. coli and Staphylococcus aureus were used,and an inoculation test microbial suspension was prepared by diluting anutrient broth medium to 1/500 using purified water to give a solutionhaving a viable cell count of 2.5 to 10×10⁵/mL. 0.4 mL of theinoculation test microbial suspension was dropped on the surface of asample, it was covered with a 4.0 cm×4.0 cm polyethylene film so as tomake uniform contact with the surface, and it was stored at atemperature of 35° C. and a humidity of 95 RH % for 24 hours. The viablecell count was measured by a standard agar pour-plate method (37° C., 2days) using a washing obtained by washing surviving cells from the topof the sample with 10 mL of cell count measurement medium (SCDLP liquidmedium) 0 hours (cell count immediately after inoculation) and 24 hoursafter starting storage, and converting into a viable cell count persheet of sample. The results of the evaluation of the antimicrobialeffects thus obtained are expressed as the difference between thelogarithm of the viable cell count of each molding plate and thelogarithm of the viable cell count of the comparative molding plate No.X for each resin, and are given in Table 2. The higher the value of thedifference, the higher the antimicrobial effect. The cell countsimmediately after inoculation were 2.0×10⁵ per plate for E. coli and3.7×10⁵ for Staphylococcus aureus, the viable cell counts forcomparative molding plate No. X were 1.5×10⁷ and 2.7×10⁵ for E. coli andStaphylococcus aureus respectively, and the viable cell counts forcomparative molding plate No. Y, which was Plate No. X after immersingit in ion-exchanged water at 50° C. for 16 hours, were 1.3×10⁷ and2.6×10⁵ for E. coli and Staphylococcus aureus respectively.

Hot Water Immersion (Hot Water Resistance Test), Antimicrobial Effect,and Color

Each molding plate was immersed in ion-exchanged water at 50° C. for 16hours. The molding plate after hot water immersion was used as a sample,and the antimicrobial activity was evaluated in the same manner asabove. The results are given in Table 2. It is possible to evaluate thehot water resistance of the antimicrobial effect by the degree to whichthe antimicrobial effect after hot water immersion decreased comparedwith the initial effect. The color of each molding plate after the hotwater resistance test was examined visually.

TABLE 2 Antimicrobial activity evaluation Antimicrobial effect Color ofInitial antimicrobial after hot water molding Type of effect (differencein immersion (difference in plate after Molding vitreous viable cellcount) viable cell count) hot water Plate antimicro- StaphylococcusStaphylococcus resistance No. bial agent E. coli aureus E. coli aureustest 1 Ex. 1 6.2<  4.4<  6.1<  4.4< Colorless 2 Ex. 2 6.2<  4.4<  6.1< 4.4< Colorless 3 Comp. 4.1  3.4 0.4 0.7 Colorless Ex. 1 4 Comp. 5.8 2.1 2.0 0.3 Colorless Ex. 2 5 Comp. 6.2< 3.7 1.6 1.9 Pale yellow Ex. 3 6Comp. 5.8  1.9 2.4 1.1 Pale yellow Ex. 4 7 Comp. 6.2<  4.4< 4.9 2.8 Darkyellow Ex. 5 8 Comp. 6.2< 3.8 1.9 0.5 Pale yellow Ex. 6 9 Comp. 6.2< 4.20.9 0.8 Pale yellow Ex. 7 10 Comp. 6.2<  4.4< 2.9 3.8 Yellow Ex. 8 11Comp. 6.2<  4.4<  6.1<  4.4< Yellow Ex. 9

The molding plates (No. 1 and 2) to which antimicrobial agents formedfrom the glasses of Examples 1 and 2 of the present invention were addedhad excellent antimicrobial properties and excellent colorationresistance.

Compared with the antimicrobial agent of the present invention, themolding plate (No. 3) to which was added the antimicrobial agent formedfrom the glass of Comparative Example 1, which contained no Ag₂O, had arather poor antimicrobial effect, and the effect after the hot waterresistance test was particularly degraded.

The molding plate (No. 4) to which was added the antimicrobial agentformed from the glass of Comparative Example 2, which had a rather lowZnO content and contained large amounts of SiO₂ and B₂O₃, also had arather poor antimicrobial effect, and the initial antimicrobial effectand the effect after the hot water resistance test, in particular towardStaphylococcus aureus, were degraded.

Compared with the antimicrobial agent of the present invention, themolding plate (No. 5) to which was added the antimicrobial agent formedfrom the glass of Comparative Example 3, which contained a large amountof SiO₂, had an initial effect, but the antimicrobial effect after thehot water resistance test deteriorated greatly. The color of the moldingplate after the hot water resistance test was slightly yellowish.

Compared with the antimicrobial agent of the present invention, themolding plate (No. 6) to which was added the antimicrobial agent formedfrom the glass of Comparative Example 4, which contained a slightlysmaller amount of B₂O₃, had a rather poor antimicrobial effect, and theantimicrobial effect after the hot water resistance test deterioratedparticularly greatly. The color of the molding plate after the hot waterresistance test was slightly yellowish.

Compared with the antimicrobial agent of the present invention, themolding plate (No. 7) to which was added the antimicrobial agent formedfrom the glass of Comparative Example 5, which contained P₂O₅ and didnot contain B₂O₃, had an adequate antimicrobial effect, but the moldingplate became yellow after the hot water resistance test.

Compared with the antimicrobial agent of the present invention, themolding plates (Nos. 8 and 9) to which were added the antimicrobialagents formed from the glasses of Comparative Examples 6 and 7, whichcontained a larger amount of an alkaline earth metal oxide or Na₂O, hadan initial antimicrobial effect, but the antimicrobial effectdeteriorated after the hot water resistance test, and the color of themolding plates was slightly yellowish.

Compared with the antimicrobial agent of the present invention, theglass of Comparative Example 8 and the glass of Comparative Example 9,which contained a larger amount of ZnO or Ag₂O respectively, werecolored, and the molding plates (Nos. 10 and 11) to which theseantimicrobial agents were added had an adequate antimicrobial effect,but the color of the molding plates was yellow.

1. A vitreous antimicrobial agent comprising, relative to 100 mass % of total glass components, 0.1 to 2 mass % of Ag₂O, 40.5 to 49 mass % of ZnO, 6 to 9.5 mass % of SiO₂, 30.5 to 39.5 mass % of B₂O₃, 2 to 10 mass % of an alkaline earth metal oxide, and 6 to 7.5 mass % of Na₂O.
 2. The vitreous antimicrobial agent according to claim 1, wherein the glass components further comprise 0.01 to 5 mass % of CeO₂.
 3. The vitreous antimicrobial agent according to claim 1, wherein the vitreous antimicrobial agent is a powder and has an average particle size of 0.1 to 30 μm.
 4. An antimicrobial resin composition comprising the vitreous antimicrobial agent according to claim 1 in an amount at which an antimicrobial function is exhibited.
 5. An antimicrobial resin composition comprising the vitreous antimicrobial agent according to claim 2 in an amount at which an antimicrobial function is exhibited.
 6. An antimicrobial resin composition comprising the vitreous antimicrobial agent according to claim 3 in an amount at which an antimicrobial function is exhibited.
 7. An antimicrobial resin composition comprising the vitreous antimicrobial agent according to claim 1 at 0.03 to 5 parts by mass relative to 100 parts by mass of the antimicrobial resin composition.
 8. An antimicrobial resin composition comprising the vitreous antimicrobial agent according to claim 2 at 0.03 to 5 parts by mass relative to 100 parts by mass of the antimicrobial resin composition.
 9. An antimicrobial resin composition comprising the vitreous antimicrobial agent according to claim 3 at 0.03 to 5 parts by mass relative to 100 parts by mass of the antimicrobial resin composition.
 10. An antimicrobial product comprising the vitreous antimicrobial agent according to claim
 1. 11. An antimicrobial product comprising the vitreous antimicrobial agent according to claim
 2. 12. An antimicrobial product comprising the vitreous antimicrobial agent according to claim
 3. 